Abstract: Focusing on doctors as the core communicators, this study develops a theoretical model based on theories of social presence, cognitive load, and media richness to investigate how multimodal features influence the dissemination effectiveness of health science short videos. Using a dataset of 2,683 health science short videos published by doctors on Douyin, we conducted regression analysis and robustness tests, integrating methods such as audio analysis, text mining, and image recognition. The study examines how video content formats and doctors' self-presentation characteristics affect dissemination effectiveness through mediating factors, including cue multiplicity, interactivity, authenticity, and emotional resonance. Results indicate that the inclusion of case analyses, evidence-based support, and highly cohesive language significantly enhances dissemination effectiveness. In contrast, explicitly prompting user interactions such as comments or likes, as well as emphasizing the doctor's professional identity or clinical setting, significantly reduces it. From the perspective of doctors' professionalism, this study clarifies the multimodal influencing mechanisms underlying the dissemination effectiveness of doctor-led health science short videos. It also enriches research perspectives on science communication via short videos, and offers practical insights for professional institutions and individuals engaged in health science popularization.

Key words: Health science popularization by doctors, Short science videos, Social presence, Cognitive load, Communication effect, Multimodal features